1. Field of the Invention
This invention relates to combustion chambers which are cooled by means of an air film, and is concerned with that type of combustion chamber comprising a dome-shaped front or end wall which is perforated in its median part to receive one or more burners, the combustion space being separated from the front wall by a shield-plate forming a heat screen to protect the end of the chamber.
2. Description of the Prior Art
In U.S. Pat. No. 3,735,589 and French Patent No. 71 33401 a combustion chamber of the type to which the present invention is directed is described which is intended especially for aircraft turbojets or other gas turbine engines where a fuel is burnt in a flow of high pressure air and where there is a serious problem of ensuring efficient cooling of the end wall in question.
A number of drawbacks have been encountered at low ratings, particularly when using prevaporization because of the low temperature of the air fed to the combustion chamber: part of the fuel streams over the end wall of the chamber or onto the shield-plate and does not take part in the combustion process. Further, at low ratings, whatever the method of injection, combustion is localized to the immediate vicinity of the cold walls at the end of the chamber and the gas reactions are rapidly frozen before complete combustion can be effected.
It is an object of the present invention to improve the combustion efficiency at reduced ratings (especially under idling conditions) by effecting atomization of any fuel which may stream over the end wall of the chamber and by locally increasing turbulence, thus promoting more efficient combustion. Any improvement of combustion efficiency under idling conditions is of significance since it affords a notable lowering of levels of pollution by carbon monoxide and unburnt hydrocarbons.